System and method for treating atrial arrhythmias

ABSTRACT

A system for defibrillating an atrial region of a heart experiencing a supraventricular arrhytmia. The defibrillation system senses and analyzes both atrial and ventricular cardiac signals of the heart to determine if the heart is experiencing a supraventricular arrhythmia. Upon detecting a supraventricular arrhythmia, the defibrillation system begins delivering a train of atrial pacing pulses to the atria of the heart and a series of ventricular pacing pulses to the ventricles of the heart to synchronize the contractions of the heart with the pacing pulses. The defibrillation system then delivers a defibrillation electrical energy pulse across the atrial region at a predetermined coupling interval time after delivering a final atrial pacing pulse and a final ventricular pacing pulse so that the defibrillation pulse will fall outside the occurrence of a T-wave of the heart, thus reducing the likelihood of inducing ventricular fibrillation.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.09/044,651, filed on Mar. 19, 1998, now U.S. Pat. No. 6,246,906 thespecification of which is incorporated herein by reference.

TECHNICAL FIELD

The present invention relates generally to implantable medical devicesand in particular to the use of implantable medical devices for treatingsupraventricular tachyarrhythmias.

BACKGROUND OF INVENTION

Clinically, atrial arrhythmias are one of the most frequentlyencountered of the cardiac arrhythmias. Annually, more than 500,000individuals are diagnosed with atrial arrhythmias, including atrialfibrillation, flutter and tachycardia. While these conditions are notimmediately life-threatening, they can lead to serious health risks ifleft untreated. These include the increased potential for developingchronic fibrillation, embolic strokes and for transferring the aberrantatrial electrical signals to the ventricles, which can result inventricular tachycardia and/or ventricular fibrillation.

Treating atrial fibrillation has traditionally involved the use ofantiarrhythmic agents. However, patients who have experienced only oneepisode or infrequent paroxysmal episodes of atrial fibrillation may notwant the inconvenience of daily medication and follow-up. Alternatively,patients with recurrent episodes are at the highest risk for athromboembolism and often are candidates for maintenance antiarrhythmicand anticoagulation therapies. This long-term therapy, however, can havepotential drawbacks as chronic use of some antiarrhytmnic agents mayhave toxic side effects. As a result, effective alternatives to chronicpharmacological treatment have been sought.

Implantable atrial cardioverter/defibrillators are a potential solutionto acutely treat atrial fibrillation. The implantable atrialcardioverter/defibrillators sense and analyze atrial cardiac signals todetect the occurrence of an atrial arrhythmia. Once an atrial arrhythmiais detected, the device can deliver a low energy discharge ofcardioverting/defibrillating electrical energy across the atria of theheart in an attempt to terminate the arrhythmia and to restore normalsinus rhythm. In designing these devices, investigators have alsoproposed synchronizing the delivery of the atrial defibrillation pulseto the sinus rhythm of the ventricles so as to avoid triggering aventricular arrhythmia. While these suggested methods attempt to preventinducing a ventricular arrhythmia, there remains the possibility ofinducing a ventricular tachyarrhythmia or a ventricular fibrillation byinadvertently delivering a cardioverting/defibrillating electricalenergy pulse during a T-wave that resulted from an aberrant ventricularcontraction. Therefore, a need still exists for a system to safely andreliably treat a supraventricular arrhythmia.

SUMMARY OF THE INVENTION

The present invention provides an improved defibrillation system andmethod for safely and reliably treating supraventricular arrhythmias.The defibrillation system and method respond to a detectedsupraventricular arrhythmia by delivering a train of atrial pacingpulses and a series of ventricular pacing pulses in a synchronizedmanner. The invention is unique in that the defibrillation systemsynchronizes and coordinates the ventricles and the atria of the heartusing the synchronized pacing pulses prior to defibrillating the atriasuch that the defibrillation electrical energy pulse is delivered so asto avoid occurring during a ventricular T-wave, thus reducing thelikelihood of inducing a ventricular tachyarrhythmia or ventricularfibrillation.

According to one embodiment of the present invention there is provided asystem including an implantable housing; a ventricular catheter; anatrial catheter; and electronic control circuitry within the implantablehousing and coupled to the ventricular and atrial catheters foridentifying and analyzing cardiac signals and for providing electricalenergy to the heart to affect sinus rhythm of the heart in response to asignal from the electronic control circuitry indicating the occurrenceof an atrial arrhythmia.

The ventricle catheter of the defibrillator system has at least oneventricular pacing electrode on its peripheral surface, which iselectrically connected to the electronic control circuitry within theimplantable housing. In one embodiment, the ventricular catheter has afirst ventricular electrode and a second ventricular electrode forsensing and pacing the ventricle of the heart. In an additionalembodiment, the ventricle catheter is positioned within the heart withthe ventricle pacing electrodes in an apex location of a right ventriclechamber of the heart.

The atrial catheter has at least one atrial pacing electrode and atleast one defibrillation electrode, both of which are electricallyconnected to the electronic control circuitry. In one embodiment, theatrial catheter has an atrial pacing electrode and a defibrillationelectrode for sensing, pacing and defibrillating the atria of the heart.In an additional embodiment, the atrial catheter is positioned in theheart with the atrial pacing electrode in a supraventricular region ofthe heart and the defibrillation electrode in the right atrium chamberor a major vein leading to the right atrium of the heart.

According to one embodiment of the method of defibrillating the atria ofthe heart, when a supraventricular arrhythmia is detected, theelectronic control circuitry delivers a synchronized pacing scheme ofatrial and ventricular pacing pulses. The synchronized pacing schemebegins with an initial concurrent atrial and ventricular pacing pulse.The defibrillation system then proceeds to deliver a synchronized trainof atrial pacing pulses through the atrial pacing electrode. In analternative embodiment, the synchronized pacing scheme begins with afirst atrial pacing pulse from the train of atrial pacing pulses beingdelivered to an atrial region of the heart upon detecting a ventricularR-wave through the ventricular catheter. Concurrent with delivering thetrain of atrial pacing pulses to the atrial region of the heart, thedefibrillation system and method also deliver a series of ventricularpacing pulses to the ventricular region of the heart through theventricular catheter.

The series of ventricular pacing pulses delivered to the ventricularregion of the heart are synchronized with the delivery of the train ofatrial pacing pulses to the atrial. The synchronization of the pacingpulses to the atrial and ventricular regions of the heart is based on a1 to “n” ratio of ventricular pacing pulses to atrial pacing pulses,where “n” is an integer value greater than or equal to 3 and less thanor equal to 50. The series of ventricular pacing pulses delivered to theventricles help to stabilize the ventricular rhythm prior to thedelivery of the atrial defibrillation electrical energy pulse.

At a predetermined coupling interval time after deliver in g a finalatrial pacing pulse and a final ventricular pacing pulse, the atrialdefibrillation electrical energy pulse is delivered across the atria ofthe heart. This atrial defibrillation pulse is timed so that thedefibrillation electrical energy pulse falls outside the occurrence of aventricular T-wave, thus reducing the chance of inducing ventricularfibrillation. As a result, the synchronized atrial defibrillation pulseof the present invention provides for a safer manner of treating atrialarrhythmias.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of one embodiment of a defibrillationsystem of the present invention with an atrial lead and a ventricularlead implanted in a human heart from which segments have been removed toshow details;

FIG. 2 is a schematic of one embodiment of electronic control circuitryaccording to the present invention;

FIG. 3 is a flow diagram of one embodiment of the method according tothe present invention;

FIG. 4 is a schematic diagram illustrating one embodiment of a timingsequence of pacing and defibrillating pulses according to the presentinvention; and

FIG. 5 is a schematic diagram illustrating one embodiment of a timingsequence of pacing and defibrillating pulses according to the presentinvention.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawings which form a part hereof and in which is shown byway of illustration specific embodiments in which the invention may bepracticed. These embodiments are described in sufficient detail toenable those skilled in the art to practice and use the invention, andit is to be understood that other embodiments may be utilized and thatelectrical, logical, and structural changes may be made withoutdeparting from the spirit and scope of the present invention. Thefollowing detailed description is, therefore, not to be taken in alimiting sense and the scope of the present invention is defined by theappended claims and their equivalents.

Referring now to FIG. 1 of the drawings, there is shown one embodimentof a defibrillation system 20 including an implantable pulse generator22 physically and electrically coupled to a ventricular catheter 24 andan atrial catheter 26, which defibrillation system 20 may be used inpracticing the method according to the present invention. Thedefibrillation system 20 is implanted in a human body 28 with portionsof the atrial catheter 26 and the ventricular catheter 24 inserted intoa heart 30 to detect and analyze electric cardiac signals produced byboth the atria 32 and the ventricles 34 of the heart 30 and to provideelectrical energy to the heart 30 under certain predetermined conditionsto treat atrial arrhythmias of the heart 30.

A schematic of the implantable pulse generator 22 electronics is shownin FIG. 2. The implantable pulse generator 22 comprises an implantablehousing 36 which contains electronic control circuitry, including amicroprocessor 100, read only memory (ROM) 102, sensing hardware 104,including sense amplifiers, therapy delivery hardware 106, including adefibrillation capacitor, and telemetry hardware 108. All electroniccomponents of the implantable pulse generator 22 are interconnected byway of a bus connection 101. Within the ROM 102 the algorithm of thepresent invention is implemented as firmware and is executed by themicroprocessor 100. The sensing hardware 104 is also connected to themicroprocessor 100, and contains a plurality of electrical connections110 coupled to the sense amplifiers. The output of the sense amplifiersis connected to the microprocessor 100, so that the atrial 32 and theventricular 34 cardiac signals received through the sensing hardware 104are analyzed by the algorithm within the microprocessor 100.

The microprocessor 100 is also coupled to the therapy delivery hardware106, which controls the delivery of electrical energy to the heart 30through a plurality of electrical output connections 112 to affect thesinus rhythm of the heart 30 under certain combinations of atrial 32 andventricular 34 conditions. Power to the implantable pulse generator 22is supplied by an electrochemical battery 114 that is housed within theimplantable pulse generator 22. The implantable pulse generator 22 isinterrogated and programmed via bidirectional radio frequency telemetrythrough the telemetry hardware 108 with an external programmer.

Referring again to FIG. 1, a connector block 38 is mounted on theimplantable pulse generator 22. In one embodiment, the connector block38 has two connector ports to physically and electrically connect theatrial catheter 26 and the ventricular catheter 24 to the sensinghardware 104 and the therapy delivery hardware 106 of the implantablepulse generator 22. Additional connector ports can be added to theconnector block 38, and configurations with three or more ports can beemployed. Alternatively, the connector block can be provided with oneconnector port for physically and electrically connecting an implantabletransvenous catheter to the implantable pulse generator 22.

The electrical activity in the heart 30 is sensed and therapies aredelivered to the heart 30 through at least one transvenous pacing anddefibrillation lead connected to the implantable pulse generator 22.Unipolar and/or bipolar pacing and sensing electrodes are used inconjunction with the at least one transvenous pacing and defibrillationlead. In the embodiment shown in FIG. 1, a bipolar lead is utilized forsensing ventricular activity and a unipolar lead is utilized for sensingatrial activity. Sensing the atrial activity includes determining theoccurrence of atrial P-waves, and sensing the ventricular activityincludes determining the occurrence of ventricular R-waves.

The defibrillation system 20 also has at least one defibrillationelectrode on the atrial catheter 26 which is connected to the pluralityof electrical output connections 112, and serves to deliverdefibrillation level, or cardioversion level, electrical pulses to theatria of the heart 30 upon a signal from the microprocessor 100indicating a predetermined condition within the heart 30. The level ofdefibrillation electrical energy pulse delivered to the atrial region ofthe heart 30 is a programmable value set between 1 to 10 Joules. Otherdefibrillation electrical energy levels are possible, however, and caninclude values that are less than 1 Joules or greater than 10 Joules.

In one embodiment, the implantable housing 36 of the defibrillationsystem 20 is a defibrillation electrode and defibrillation electricalpulses are delivered to the atria between the defibrillation electrodeon the atrial catheter 26 and the implantable housing 36 of theimplantable pulse generator 22. In one embodiment, the implantablehousing 36 of the implantable pulse generator 22 has an exposedelectrically conductive surface that is electrically connected to ananode of the therapy delivery hardware 106. All defibrillationelectrical pulses are delivered to the heart with at least twodefibrillation electrodes, or through at least one defibrillationelectrode and the implantable housing 36 of the implantable pulsegenerator 22 where the defibrillating electrical energy provided to thepatient's heart is a biphasic pulse delivered between the exposedelectrically conductive surface of the implantable housing and thedefibrillation electrode. Additionally, the biphasic pulses deliveredbetween exposed electrically conductive surface of the implantablehousing and the defibrillation electrode are asymmetric with a firstphase of the biphasic pulse having a greater amplitude than the secondphase of the biphasic pulse. The defibrillation system 20 also supportsa plurality of sensing and pacing regimens for both the atria and theventricles, including DDDR pacing, which are known in the art.

Referring now to FIG. 1, there is shown an embodiment of the ventricularcatheter 24 having an elongate body 40, a peripheral surface 42,proximal and distal ends, 44 and 46, and at least one ventricular pacingelectrode connected to the electronic control circuitry. In oneembodiment, the ventricular catheter 24 has a first ventricularelectrode 48 and a second ventricular electrode 50 on the peripheralsurface 42. The first ventricular electrode 48 and the secondventricular electrode 50 receive bipolar electrical cardiac signals froma right ventricular chamber 52 of the heart 30, and are attached on theperipheral surface 42 of the elongate body 40.

The first ventricular electrode 48 is at or adjacent to the distal end46 of the elongate body 40 and is either a pacing tip electrode or asemi-annular electrode partially encircling or an annular electrodeencircling the peripheral surface 42 of the elongate body 40. The secondventricular electrode 50 is an annular electrode encircling or asemi-annular electrode partially encircling the peripheral surface 42 ofthe elongate body 40. The second ventricular electrode 50 is spacedlongitudinally along the peripheral surface 42 from the firstventricular electrode 48 and the distal end 46 of the ventricularcatheter 24 is positioned within the right ventricular chamber 52 of theheart 30 with the first ventricular electrode 48, in one embodiment,located in an apex location of the right ventricular chamber 52 of theheart 30.

Electrical leads extend longitudinally within the elongate body 40 ofthe ventricular catheter 24 from a connection end at the proximal end 44and make connection to the first and second ventricular electrodes 48and 50. The proximal end 44 of the ventricular catheter 24 is releasablyattached to the connector block 38 of the implantable pulse generator 22with the contact ends of the electrical leads in electrical connectionwith both the sense amplifiers of the sensing hardware 104 and thetherapy delivery hardware 106 such that the implantable pulse generatorreceives bipolar signals from and delivers bipolar pacing to the rightventricular chamber 52 of the heart 30.

In a further embodiment, the atrial catheter 26 is shown comprising anelongate body 54 having a peripheral surface 56, a proximal end 58, adistal end 60, and at least one atrial pacing electrode and at least onedefibrillation electrode, both of which are located on the peripheralsurface 56 of the elongate body 54. Referring to FIG. 1, there is shownone embodiment of the atrial catheter 26 having an atrial pacingelectrode 62 and a defibrillation electrode 64. In one embodiment, thedefibrillation electrode 64 is a defibrillation coil electrode as areknown in the art. The atrial pacing electrode 62 is at or adjacent thedistal end of the elongate body 54 where it receives unipolar electricalcardiac signals from a right atrial chamber 68 of the heart 30.

Both the atrial pacing electrode 62 and the defibrillation electrode 64are attached on the peripheral surface of the elongate body 54 where thedefibrillation electrode 64 is spaced apart and spaced longitudinallyfrom the atrial pacing electrode 62 on the peripheral surface 56 of theatrial catheter 26. In one embodiment, the atrial catheter 26 ispositioned within the heart 30 with the atrial pacing electrode 62 andthe defibrillation electrode 64 in the supraventricular region of theheart 30, where the distal end 60 of the atrial catheter 26 is locatedwithin the right atrial chamber 68 of the heart 30 to afford positioningthe atrial pacing electrode 62 on an endocardial wall of the rightatrial chamber 68 and the defibrillation electrode 64 positioned withinthe right atrial chamber 68 or a major vein leading to the right atriumof the patient's heart. Suitable location for the atrial pacingelectrode 62 includes the right atrial appendage, high right atrium orcoronary sinus os. Alternatively, the distal end 60 of the atrialcatheter 26 is located within a coronary vein of the patient's heart,including a coronary sinus or a great vein, to position the atrialpacing electrode 62 adjacent to the left atrium chamber of the heart 30,and the defibrillation electrode 64 within the right atrial chamber 68or a major vein leading to right atrium.

In an alternate embodiment, the atrial catheter has a second atrialpacing electrode attached to the peripheral surface of the elongate bodywhere the first atrial pacing electrode 62 is at or adjacent to thedistal end 60 of the elongate body 54 and is either a pacing tipelectrode or a semi-annular electrode partially encircling or an annularelectrode encircling the peripheral surface 56 of the elongate body 54.The second atrial pacing electrode is an annular electrode encircling orsemi-annular electrode partially encircling the peripheral surface 56 ofthe elongate body 54 and allows the defibrillation system 20 to providebipolar sensing and pacing to the supraventricular region of the heart30.

In an additional embodiment, the atrial catheter 26 includes twodefibrillation electrodes on the peripheral surface 56 of the elongatebody 54 where the two defibrillation electrodes are spaced apart andspaced longitudinally along the peripheral surface 56 of the atrialcatheter 26 to afford positioning the atrial catheter 26 within thecoronary sinus of the patient's heart 30 with the atrial pacingelectrode 62 and the two defibrillation electrodes within thesupraventricular region of the patient's heart. In one embodiment, theatrial pacing electrode 62 is adjacent to the left atrial chamber of theheart 30, one of the two defibrillation electrodes within the coronarysinus of the heart 30, and the second defibrillation electrode withinthe right atrial chamber 68 or a major vein leading to right atrialchamber 68 of the heart 30.

Besides the lead configuration shown in FIG. 1, the defibrillationsystem 20 supports several other lead configurations and types. Forexample it is possible to use ventricular epicardial rate sensing,atrial endocardial bipolar pace/sensing, ventricular endocardial bipolarpace/sensing, epicardial patches, single body transvenous leads with twoor more defibrillation electrodes and at least one pacing electrode, andancillary leads in conjunction with the implantable pulse generator 22.

In one embodiment, the defibrillating electrical energy provided to thepatient's heart are biphasic pulses delivered between the defibrillationelectrode 64 and the implantable housing 36 of the implantable pulsegenerator 22. In an alternative embodiment, the defibrillatingelectrical energy provided to the heart are biphasic pulses deliveredbetween the two defibrillation electrodes. In a further embodiment, thetwo defibrillation electrodes are electrically connected such that thedefibrillating electrical energy provided to the heart are biphasicpulses delivered between the electrically connected defibrillationelectrodes and the exposed electrically conductive surface of theimplantable housing 36.

Referring once again to FIG. 1, electrical leads extend longitudinallywithin the elongate body 54 of the atrial catheter 26 from a connectionend at the proximal end 58 to make connection with the atrial pacingelectrode 62 and the defibrillation electrode 64. The proximal end 58 ofthe atrial catheter 26 is releasably attached to the connector block 38of the implantable pulse generator 22 with the contact ends of theelectrical leads in electrical connection with the electronic controlcircuitry, including both the sense amplifiers of the sensing hardware104 and the therapy delivery hardware 106 such that the implantablepulse generator 22 receives unipolar signals from the atria 32 of theheart 30 and delivers unipolar pacing and defibrillation electricalenergy pulses to the atria 32 of the heart 30.

The ventricular catheter 24 and the atrial catheter 26 are releasablyattached to and are separated from the implantable pulse generator 22 tofacilitate inserting the ventricular catheter 24 and the atrial catheter26 into the heart 30. The ventricular and atrial catheters, 24 and 26,are inserted into the heart 30 transvenously through a cephalic orsubclavian vein to position the distal end 46 of the atrial catheter 26in the supraventricular region of the heart 30 and the distal end 60 ofthe ventricular catheter 24 in the apex of the right ventricular chamber52. The proximal end 44 of the atrial catheter 26 and the proximal endof the ventricular catheter 24 are then attached to the implantablepulse generator 22. The proximal end 44 of the atrial catheter 26 andthe proximal end 58 of the ventricular catheter 24 are adapted to sealtogether with the connector ports of the implantable pulse generator 22to thereby engage the contact ends of the atrial catheter 26 and theventricular catheter 24 with the plurality of electrical connections 110and the therapy delivery hardware 106 of the implantable pulse generator22. The implantable pulse generator 22 of the defibrillation system 20is then positioned subcutaneously within the human body 28.

Referring now to FIG. 3, there is shown a flow diagram of one embodimentof the method used by the defibrillation system 20 for treating asupraventricular arrhythmia of a patient's heart. Initially at 300, thedefibrillation system 20 utilizes the ventricular catheter 24 and theatrial catheter 26 for sensing the ventricular and atrial cardiacsignals of the heart 30. The electronic control circuitry receiveseither unipolar or bipolar cardiac signals through the ventricular andatrial pacing electrodes. The sensed cardiac signals are then analyzedby the defibrillation system 20 at 310 to determine if the heart isexperiencing a supraventricular arrhythmia. In this context asupraventricular arrhythmia can include atrial tachyarrhythmias andatrial fibrillation.

In one embodiment, the electronic control circuitry of thedefibrillation system 20 determines the occurrence and/or presence ofsupraventricular arrhythmias at 310 by analyzing the structure of theP-wave detected by the defibrillation system 20. In an alternativeembodiment, the rate relation of the atrial P-waves and the ventricularR-waves is used to determine if the heart 30 is experiencing asupraventricular arrhythmia. In one embodiment, the presence of anatrial fibrillation is indicated when the defibrillation system 20detects both an atrial rate that is greater than 200 beats per minuteand the absence of a ventricular arrhythmia. In one embodiment, theabsence of a ventricular arrhythmia is indicated when the ventricularrate is less than 150 beats per minute as detected by the ventricularcatheter 24.

During 310, if the heart is not experiencing a supraventriculararrhythmia, the defibrillation system 20 returns to 300 to analyze thenext series of sensed ventricular and atrial intervals. If, however, asupraventricular arrhythmia is detected at 310, the defibrillationsystem 20 proceeds to 320 where the electronic control circuitry of thedefibrillation system 20 functions to deliver the synchronized atrialand ventricular pacing pulses over a programmable pacing schemeduration. In one embodiment, the programmable pacing scheme duration isthe time during which the synchronized atrial and ventricular pacingpulses are delivered to the heart 30. During the programmable pacingscheme duration, the defibrillation system 20 charges the defibrillationcapacitor to a predetermined energy level. At the conclusion of theprogrammable pacing scheme duration the therapy delivery hardware 106 isthen prepared to deliver at least one atrial defibrillation level shockto the supraventricular region of the heart 30. The programmable pacingscheme duration is a programmable value that is set in the range between2 to 30 seconds.

At the beginning of the programmable pacing scheme duration, thedefibrillation system 20 starts the synchronized atrial and ventricularpacing pulses by delivering a train of atrial pacing pulses to an atrialregion of the heart and a series of ventricular pacing pulses to aventricular region of the heart, where the series of ventricular pacingpulses is synchronized with the train of atrial pacing pulses. In oneembodiment, the delivery of the synchronized train of atrial pacingpulses and the series of ventricular pacing pulses begin with an initialconcurrent atrial and ventricular pacing pulse. In an alternativeembodiment, the delivery of the synchronized atrial and ventricularpacing pulses begins with the defibrillation system 20 initiallydelivering a first atrial pacing pulse of the train of atrial pacingpulses. A first ventricular pacing pulse synchronized with the train ofatrial pacing pulses is then subsequently delivered to the heart. In oneembodiment, the first atrial pacing pulse of the train of atrial pacingpulses is delivered during a ventricular R-wave detected by thedefibrillation system 20.

The electronic control circuitry is programmed to deliver a set numberof atrial pacing pulses during the train of atrial pacing pulses, wherethe number of atrial pacing pulses is programmed in the range of betweenapproximately 10 to 1000 pacing pulses. Additional ranges for the numberof atrial pacing pulses are also possible, for example the number ofatrial pacing pulses can be selected from the ranges of between 20 to 70or 30 to 50 pacing pulses. The atrial pacing pulses of the train ofatrial pacing pulses are also delivered to the atrium at a programmableatrial pacing interval. The programmable atrial pacing interval is setto a value between approximately 20 to 50 milliseconds per pacing pulse.Other programmable atrial pacing interval ranges are possible, however,and by way of example can include values between 25 to 50, 25 to 45, 20to 40, or 30 to 40 milliseconds per atrial pacing pulse.

In one embodiment, the defibrillation system 20 delivers the train ofatrial pacing pulses across the atrial pacing electrode 62 to an atrialregion of the heart 30. The energy level of the pacing pulses of thetrain of atrial pacing pulses are a programmable value set between 0.01to 1 Joules. Other pacing pulse energy levels are possible, however, andcan include values that are less than 0.01 or greater than 1 Joules.

Concurrent with the delivery of the train of atrial pacing pulses, theelectronic control circuitry of the defibrillation system 20 at step 330also delivers a series of ventricular pacing pulses across theventricular pacing electrodes to a ventricular region of the heart 30.In one embodiment, the pacing rate of the series of the ventricularpacing pulses is a programmable value, where the ventricular pacing rateis programmed at a pacing rate that is at least 10 beats per minuteabove the patient's intrinsic ventricular rate. The concurrent deliveryof the series of ventricular pacing pulses is synchronized with thetrain of atrial pacing pulses. In one embodiment, to synchronize theventricular and atrial pacing pulses, each ventricular pacing pulse ofthe series of ventricular pacing pulses is synchronized to occur withevery nth atrial pacing pulse of the train of atrial pacing pulses,where n is a programmable integer value greater than or equal to 3 andless than or equal to 50. The number of atrial pacing pulses in thetrain of atrial pacing pulses must also be divisible by n such that theresult is an integer value (e.g., atrial train equal to 50, n equal to 5and ventricular series equal to 10 pacing pulses). This synchronizedpacing scheme allow the defibrillation system 20 to issue a concurrentatrial and ventricular pacing pulse every n atrial pacing pulse, andallows for a final atrial pacing pulse of the train of atrial pacingpulses and a final ventricular pacing pulse to be delivered to theheart.

In one embodiment, the final atrial pacing pulses and the finalventricular pacing pulse are delivered substantially simultaneously tothe heart. This synchronization of the atrial and ventricular pacingpulse trains organizes and synchronizes the contraction of both theatria and the ventricles of the heart 30 in such a way that ventricularpacing pulses and a subsequent atrial defibrillation electrical energypulse is delivered to the heart outside of a ventricular T-wave, thusreducing the likelihood of inducing ventricular fibrillation.

In one embodiment of the present invention, the term substantiallysimultaneously constitutes pacing pulses that are delivered within atleast 5 ms of each other. However, in an alternative embodiment, a delayin delivering the final atrial and final ventricular pacing pulse isprogrammed into the defibrillation system, such that the finalventricular pacing pulse is delivered prior to delivering the finalatrial pacing pulse. This programmed delay in delivering the finalatrial and final ventricular pulse is programmed by the physician orclinician into the defibrillation system base up each individualpatient's cardiological condition.

In an additional embodiment, the defibrillation system 20 monitors theventricular region of the heart prior to delivering the final concurrentatrial and ventricular pacing pulse to determine if a prematureventricular contraction has occurred. In this context, a prematureventricular contraction is any ventricular contraction, indicated by asensed R-wave, that occurs subsequent to the most recently pacedventricular contraction. In other words, the defibrillation system 20monitors the heart 30 to ensure that a previously detected ventricularR-wave was the result of a ventricular pacing pulse delivered by thedefibrillator system 20, and not the result of a premature ventricularcontraction. This consideration may be important as it has beensuggested that if the R-wave interval just prior to delivering an atrialdefibrillation shock was too short in duration, possibly due to apremature ventricular contraction, the chances of inducing a ventriculararrhythmia from the shock may be higher.

If the most recently detected R-wave just prior to delivering the atrialdefibrillation shock was a premature ventricular contraction, thedefibrillation system 20 in one embodiment repeats the entire pacingscheme of delivering the train of atrial pacing pulses to the atrialregion of the heart 30 and the series of ventricular pacing pulses to aventricular region of the heart 30 again. In an alternative embodiment,the defibrillation system 20 delivers a predetermined number ofadditional atrial pacing pulses and ventricular pacing pulses to theheart 30 upon detecting a premature ventricular contraction. Thedefibrillation system 20 delivers the additional atrial and ventricularpacing pulses according to the same synchronized pacing scheme used indelivering the train of atrial pacing pulses and the series ofventricular pacing pulses. Upon completing delivery of the additionalatrial and ventricular pacing pulses, the defibrillation system 20monitors the ventricular region of the heart 30 prior to delivering thefinal atrial pacing pulse and the final ventricular pacing pulse todetermine if a premature ventricular contraction has occurred. Thepredetermined number of additional atrial pacing pulses is aprogrammable number set in the range between 10 to 1000 pacing pulses,and the number of additional ventricular pacing pulses are determined byand are synchronized to occur with every nth pacing pulse of theadditional atrial pacing pulses, where n is a programmable integer valuegreater than or equal to 3 and less than or equal to 50.

After the synchronized atrial and ventricular pacing pulses have beendelivered to the heart 30, the defibrillation system 20 terminates thesupraventricular arrhythmia at step 340 by delivering a defibrillationpulse of electrical energy at a predetermined coupling interval timeafter the final concurrent atrial pacing pulse and ventricular pacingpulse across the atria 32 region of the heart 30.

In one embodiment, the defibrillation pulse of electrical energy isdelivered to the atria between the defibrillation electrode 64 and theimplantable housing 36 of the implantable pulse generator 22. Deliveringthe defibrillation electrical energy pulse at the predetermined couplinginterval time after delivering a final atrial pacing pulse and a finalventricular pacing pulse ensures that the defibrillation electricalenergy pulse will fall outside the occurrence of a ventricular T-wave ofthe heart, and will thus reduce the likelihood of inducing a ventricularfibrillation.

The predetermined coupling interval time after delivering the finalatrial pacing pulse and the final ventricular pacing pulse is aprogrammable value of between approximately 20 to 150 milliseconds,where 85 milliseconds is an appropriate value. The predeterminedcoupling interval time, however, is not limited to the aforementionedrange, and values outside of this range exist which do not depart fromthe scope of the invention.

Referring now to FIG. 4, there is shown a schematic diagram illustratingone embodiment of a timing sequence of pacing and defibrillationelectrical energy pulse being delivered to a heart experiencing asupraventricular arrhythmia according to the present invention. Thetrain of atrial pacing pulses is programmed to deliver forty (40) atrialpacing pulses at an interval time between each pacing pulse of 100 msand is represented by line A of FIG. 4. The programmable pacing schemeduration is programmed to 4 seconds, and the integer value for n isprogrammed to 4, such that the defibrillation system 20 will deliver theventricular pacing pulse to the heart with every fourth atrial pacingpulse delivered. Ventricular pacing pulses are shown on line B of FIG.4. Line C of FIG. 4 is a schematic of an electrocardiogram representingthe paced cardiac rhythm of the heart 30.

Upon detecting a supraventricular arrhythmia, the electronic controlcircuitry of the defibrillation system 20 starts the train of atrialpacing pulses at 400 during a detected R-wave. The atrial pacing pulsesshown at line A are delivered at a 100 ms interval and at 410 a firstventricular pacing pulse is delivered to the ventricles about 400 msafter the start of the train of atrial pacing pulses. This pacing schemereduces the likelihood of the first ventricular pacing pulse fromfalling on a ventricular T-wave, as the ventricular T-wave typicallyoccurs about 120 milliseconds after the ventricular R-wave.Subsequently, a ventricular pacing pulse is delivered on every fourthatrial pulse of the train which effectively drives the ventricle at a4:1 rate of the atrial pacing rate.

The defibrillation system 20 proceeds to deliver the synchronized seriesof atrial and ventricular pacing pulses until a final atrial pacingpulse at 420 and a final ventricular pacing pulse at 430 is delivered onthe fortieth atrial pacing pulse and the tenth ventricular pacing pulse.In one embodiment, the final atrial pacing pulses and the finalventricular pacing pulse delivered at 430 are delivered substantiallysimultaneously to the heart. Then, at a predetermined coupling intervaltime of 85 milliseconds after delivering a final atrial pacing pulse anda final ventricular pacing pulse, the defibrillation system 20 deliversa defibrillation electrical energy pulse at 440 across the atrial regionof the patient's heart 30.

Referring now to FIG. 5, there is shown a schematic diagram illustratingan additional embodiment of a timing sequence of pacing anddefibrillation electrical energy pulse being delivered to a heartexperiencing a supraventricular arrhythmia according to the presentinvention. The train of atrial pacing pulses is programmed to deliverone hundred (100) atrial pacing pulses at an interval time between eachpacing pulse of 50 ms and is represented by line A of FIG. 5. Theprogrammable pacing scheme duration is programmed to 5 seconds, and theinteger value for n is programmed to 10, such that the defibrillationsystem 20 will deliver the ventricular pacing pulse to the heart withevery tenth atrial pacing pulse delivered. Ventricular pacing pulses areshown on line B of FIG. 5. Line C of FIG. 5 is a schematic of anelectrocardiogram representing the paced cardiac rhythm of the heart 30.

Upon detecting a supraventricular arrhythmia, the electronic controlcircuitry of the defibrillation system 20 starts the synchronized atrialand ventricular pacing pulses by delivering an initial concurrent atrialand ventricular pacing pulses at 500. The atrial pacing pulses shown online A are delivered at a 50 milliseconds and ventricular pacing pulsesare subsequently delivered on every tenth atrial pulse of the trainwhich effectively drives the ventricle at a 10:1 rate of the atrialpacing rate.

The defibrillation system 20 proceeds to deliver the synchronized seriesof atrial and ventricular pacing pulses until a final atrial pacingpulse at 520 and a final ventricular pacing pulse at 530 is delivered onthe one hundred atrial pacing pulse and the eleventh ventricular pacingpulse. In one embodiment, the final atrial pacing pulses and the finalventricular pacing pulse delivered at 530 are delivered substantiallysimultaneously to the heart. Then, at a predetermined coupling intervaltime of 85 milliseconds after delivering a final atrial pacing pulse anda final ventricular pacing pulse, the defibrillation system 20 deliversa defibrillation electrical energy pulse at 540 across the atrial regionof the patient's heart 30.

We claim:
 1. A device, comprising: a ventricular catheter with at leastone electrode adapted for being operably positioned in or near aventricle of a heart; an atrial catheter with at least one electrodeadapted for being operably positioned in or near an atrium of the heart;and electronic circuitry, including therapy delivery hardware forproducing a series of atrial pacing pulses from the atrial catheter, forproducing a series of ventricular pacing pulses from the ventricularcatheter, and for producing a defibrillation pulse from the atrialcatheter after delivering the series of atrial pacing pulses and theseries of ventricular pacing pulses, wherein the series of atrial pacingpulses and the series of ventricular pacing pulses are produced inpreparation for the defibrillation pulse.
 2. The device of claim 1,wherein the therapy delivery hardware is adapted for synchronizing theseries of atrial pacing pulses and the series of ventricular pacingpulses.
 3. The device of claim 2, wherein the therapy delivery hardwareis adapted for delivering an initial concurrent atrial and ventricularpulse.
 4. The device of claim 2, wherein the therapy delivery hardwareis adapted for delivering a first atrial pacing pulse for the series ofatrial pacing pulses and subsequently delivering a first ventricularpacing pulse for the series of ventricular pacing pulses that issynchronized with the series of atrial pacing pulses.
 5. The device ofclaim 2, wherein: the therapy delivery hardware is adapted fordelivering a ventricular pacing pulse for every n atrial pacing pulses;and the electronic circuitry provides the ability to store aprogrammable integer value for n.
 6. The device of claim 1, wherein: thetherapy delivery hardware is adapted for delivering the series of atrialpacing pulses and the series of ventricular pacing pulses over a pacingscheme duration; and the electronic circuitry provides the ability tostore a programmable value for the pacing scheme duration.
 7. The deviceof claim 1, wherein: the therapy delivery hardware is adapted fordelivering a predetermined number of atrial pacing pulses in the seriesof atrial pacing pulses; and the electronic circuitry provides theability to store a programmable value for the number of atrial pulses.8. The device of claim 1, wherein: the therapy delivery hardware isadapted for delivering the series of atrial pacing pulses at apredetermined pulse interval; and the electronic circuitry provides theability to store a programmable value for the predetermined pulseinterval.
 9. The device of claim 1, wherein: the therapy deliveryhardware is adapted for delivering the series of atrial pacing pulseswith a predetermined energy level; and the electronic circuitry providesthe ability to store a programmable value for the predetermined energylevel.
 10. The device of claim 1, wherein: the therapy delivery hardwareis adapted for delivering the series of ventricular pacing pulses at apredetermined rate; and the electronic circuitry provides the ability tostore a programmable value for the predetermined rate.
 11. The device ofclaim 1, wherein: the therapy delivery hardware is adapted fordelivering a defibrillation pulse to the heart at a predeterminedcoupling interval after delivering a final atrial pacing pulse in theseries of atrial pacing pulses and a final ventricular pacing pulse inthe series of ventricular pacing pulses; and the electronic circuitryprovides the ability to store a programmable value for the predeterminedcoupling interval.
 12. The device of claim 11, wherein the electroniccircuitry further includes sensing hardware for detectingsupraventricular tachyarrhythmia.
 13. The device of claim 12, wherein:the sensing hardware is further adapted for detecting a prematureventricular contraction; and the therapy delivery hardware is furtheradapted for delivering the series of atrial pacing pulses and the seriesof ventricular pacing pulses to the heart again prior to delivering thedefibrillation pulse to the heart when the sensing hardware detects apremature ventricular contraction.
 14. The device of claim 12, wherein:the sensing hardware is further adapted for detecting a prematureventricular contraction; the therapy delivery hardware is furtheradapted for delivering a predetermined number of additional atrialpacing pulses and ventricular pacing pulses to the heart prior todelivering the defibrillation pulse to the heart when the sensing harddetects a premature ventricular contraction; and the electroniccircuitry provides the ability to store a programmable value for thepredetermined number of additional atrial pacing pulses and ventricularpacing pulses.
 15. A method, comprising: delivering a series of atrialpacing pulses and a series of ventricular pacing pulses to a heart thatis experiencing supraventricular tachyarrhythmia; and after deliveringthe series of atrial pacing pulses and the series of ventricular pacingpulses to the heart, delivering a defibrillation pulse to the heart,wherein the series of atrial pacing pulses and the series of ventricularpacing pulses are delivered to the heart in preparation for thedefibrillation pulse.
 16. The method of claim 15, wherein delivering aseries of atrial pacing pulses and a series of ventricular pacing pulsesto a heart that is experiencing supraventricular tachyarrhythmiaincludes synchronizing the series of atrial pacing pulses and the seriesof ventricular pacing pulses.
 17. The method of claim 16, whereinsynchronizing the series of atrial pacing pulses and the series ofventricular pacing pulses includes delivering an initial concurrentatrial and ventricular pacing pulse.
 18. The method of claim 16, whereinsynchronizing the series of atrial pacing pulses and the series ofventricular pacing pulses includes delivering a first atrial pacingpulse for the series of atrial pacing pulses and subsequently deliveringa first ventricular pacing pulse for the series of ventricular pacingpulses that is synchronized with the series of atrial pacing pulses. 19.The method of claim 18, wherein delivering a first atrial pacing pulsefor the series of ventricular pacing pulses includes delivering a firstatrial pacing pulse during a detected ventricular R-wave.
 20. The methodof claim 16, wherein synchronizing the series of atrial pacing pulsesand the series of ventricular pacing pulses includes delivering aventricular pacing pulse for every programmable n atrial pacing pulses.21. The method of claim 16, wherein synchronizing the series of atrialpacing pulses and the series of ventricular pacing pulses includesdelivering a final atrial pacing pulse and a final ventricular pacingpulse substantially simultaneously.
 22. The method of claim 15, whereindelivering a series of atrial pacing pulses and a series of ventricularpacing pulses to a heart that is experiencing supraventriculartachyarrhythmia includes delivering the series of atrial pacing pulsesand the series of ventricular pacing pulses over a programmable pacingscheme duration.
 23. The method of claim 22, wherein delivering theseries of atrial pacing pulses and the series of ventricular pacingpulses over a programmable pacing scheme duration includes deliveringthe series of atrial pacing pulses and the series of ventricular pacingpulses over a programmable range between 2 and 30 seconds.
 24. Themethod of claim 15, wherein delivering a series of atrial pacing pulsesand a series of ventricular pacing pulses to a heart that isexperiencing supraventricular tachyarrhythmia includes delivering aprogrammable number of atrial pulses.
 25. The method of claim 24,wherein delivering a programmable number of atrial pulses includesdelivering a number of atrial pulses in the range between 10 and 1000pulses.
 26. The method of claim 24, wherein delivering a programmablenumber of atrial pulses includes delivering a number of atrial pulses inthe range between 20 and 70 pulses.
 27. The method of claim 24, whereindelivering a programmable number of atrial pulses includes delivering anumber of atrial pulses in the range between 30 to 50 pulses.
 28. Themethod of claim 15, wherein delivering a series of atrial pacing pulsesand a series of ventricular pacing pulses to a heart that isexperiencing supraventricular tachyarrhythmia includes delivering aseries of atrial pacing pulses at a programmable interval.
 29. Themethod of claim 28, wherein delivering atrial pulses at a programmableinterval includes delivering atrial pulses at a programmable intervalbetween 20 and 50 milliseconds per pacing pulse.
 30. The method of claim15, wherein delivering a series of atrial pacing pulses and a series ofventricular pacing pulses to a heart that is experiencingsupraventricular tachyarrhythmia includes delivering atrial pacingpulses with a programmable energy level.
 31. The method of claim 15,wherein delivering a series of atrial pacing pulses and a series ofventricular pacing pulses to a heart that is experiencingsupraventricular tachyarrhythmia includes delivering ventricular pacingpulses at a programmable rate.
 32. The method of claim 31, whereindelivering ventricular pacing pulses at a programmable rate includedelivering ventricular pacing pulses at a pacing rate that is at least10 beats per minute above an intrinsic ventricular rate.
 33. The methodof claim 15, further including monitoring the heart to detect apremature ventricular contraction.
 34. The method of claim 33, furtherincluding, upon detecting a premature ventricular contraction,delivering the series of atrial pacing pulses and the series ofventricular pacing pulses to the heart again prior to delivering thedefibrillation pulse to the heart.
 35. The method of claim 33, furtherincluding, upon detecting a premature ventricular contraction,delivering a programmable number of additional atrial pacing pulses andventricular pacing pulses to the heart prior to delivering thedefibrillation pulse to the heart.
 36. The method of claim 15, furtherincluding analyzing ventricular and atrial cardiac signals to detectsupraventricular tachyarrhythmia.
 37. The method of claim 15, whereindelivering a defibrillation pulse to the heart after delivering theatrial pacing pulses and ventricular pacing pulses to the heart includesdelivering the defibrillation pulse to the heart at a predeterminedcoupling interval after delivering a final atrial pacing pulse in theseries of atrial pacing pulses and a final ventricular pacing pulse inthe series of ventricular pacing pulses.
 38. The method of claim 37,wherein delivering the defibrillation pulse to the heart at apredetermined coupling interval occurs outside of a ventricular T-wavewhich reduces the likelihood of inducing ventricular fibrillation. 39.The method of claim 37, wherein delivering the defibrillation pulse tothe heart at a predetermined coupling interval includes delivering thedefibrillation pulse to the heart at a programmable range between 20 and150 milliseconds after delivering the final atrial pacing pulse and thefinal ventricular pacing pulse.
 40. The method of claim 37, whereindelivering the defibrillation pulse to the heart at a predeterminedcoupling interval time includes delivering a programmable electricalenergy pulse between 1 and 10 Joules.
 41. A device, comprising: aventricular catheter with at least one electrode adapted for beingoperably positioned in or near a ventricle of a heart; an atrialcatheter with at least one electrode adapted for being operablypositioned in or near an atrium of the heart; and electronic circuitry,including therapy delivery hardware for producing a series of atrialpacing pulses from the atrial catheter, for producing a series ofventricular pacing pulses from the ventricular catheter, forsynchronizing the series of atrial pacing pulses and the series ofventricular pacing pulses, for delivering an initial concurrent atrialand ventricular pulse, and for producing a defibrillation pulse from theatrial catheter after delivering the series of atrial pacing pulses andthe series of ventricular pacing pulses.
 42. A device, comprising: aventricular catheter with at least one electrode adapted for beingoperably positioned in or near a ventricle of a heart; an atrialcatheter with at least one electrode adapted for being operablypositioned in or near an atrium of the heart; and electronic circuitry,including therapy delivery hardware for producing a series of atrialpacing pulses from the atrial catheter, for producing a series ofventricular pacing pulses from the ventricular catheter, forsynchronizing the series of atrial pacing pulses and the series ofventricular pacing pulses, for delivering a first atrial pacing pulsefor the series of atrial pacing pulses and subsequently delivering afirst ventricular pacing pulse for the series of ventricular pacingpulses that is synchronized with the series of atrial pacing pulses, andfor producing a defibrillation pulse from the atrial catheter afterdelivering the series of atrial pacing pulses and the series ofventricular pacing pulses.
 43. A device, comprising: a ventricularcatheter with at least one electrode adapted for being operablypositioned in or near a ventricle of a heart; an atrial catheter with atleast one electrode adapted for being operably positioned in or near anatrium of the heart; and electronic circuitry, including therapydelivery hardware for producing a series of atrial pacing pulses fromthe atrial catheter, for producing a series of ventricular pacing pulsesfrom the ventricular catheter, and for producing a defibrillation pulsefrom the atrial catheter after delivering the series of atrial pacingpulses and the series of ventricular pacing pulses, wherein the therapydelivery hardware is adapted for delivering the series of atrial pacingpulses with a predetermined energy level, and the electronic circuitryprovides the ability to store a programmable value for the predeterminedenergy level.
 44. A device, comprising: a ventricular catheter with atleast one electrode adapted for being operably positioned in or near aventricle of a heart; an atrial catheter with at least one electrodeadapted for being operably positioned in or near an atrium of the heart;and electronic circuitry, including therapy delivery hardware forproducing a series of atrial pacing pulses from the atrial catheter, forproducing a series of ventricular pacing pulses from the ventricularcatheter, for producing a defibrillation pulse from the atrial catheterafter delivering the series of atrial pacing pulses and the series ofventricular pacing pulses, and for delivering the defibrillation pulseto the heart at a predetermined coupling interval after delivering afinal atrial pacing pulse in the series of atrial pacing pulses and afinal ventricular pacing pulse in the series of ventricular pacingpulses, wherein the electronic circuitry provides the ability to store aprogrammable value for the predetermined coupling interval.
 45. Thedevice of claim 44, wherein the electronic circuitry further includessensing hardware for detecting supraventricular tachyarrhythmia.
 46. Thedevice of claim 45, wherein: the sensing hardware is further adapted fordetecting a premature ventricular contraction; and the therapy deliveryhardware is further adapted for delivering the series of atrial pacingpulses and the series of ventricular pacing pulses to the heart againprior to delivering the defibrillation pulse to the heart when thesensing hardware detects a premature ventricular contraction.
 47. Thedevice of claim 45, wherein: the sensing hardware is further adapted fordetecting a premature ventricular contraction; the therapy deliveryhardware is further adapted for delivering a predetermined number ofadditional atrial pacing pulses and ventricular pacing pulses to theheart prior to delivering the defibrillation pulse to the heart when thesensing hard detects a premature ventricular contraction; and theelectronic circuitry provides the ability to store a programmable valuefor the predetermined number of additional atrial pacing pulses andventricular pacing pulses.
 48. A method, comprising: delivering a seriesof atrial pacing pulses and a series of ventricular pacing pulses to aheart that is experiencing supraventricular tachyarrhythmia, whichincludes synchronizing the series of atrial pacing pulses and the seriesof ventricular pacing pulses, which includes delivering an initialconcurrent atrial and ventricular pacing pulse; and after delivering theseries of atrial pacing pulses and the series of ventricular pacingpulses to the heart, delivering a defibrillation pulse to the heart. 49.A method, comprising: delivering a series of atrial pacing pulses and aseries of ventricular pacing pulses to a heart that is experiencingsupraventricular tachyarrhythmia, which includes synchronizing theseries of atrial pacing pulses and the series of ventricular pacingpulses, which includes delivering a first atrial pacing pulse for theseries of atrial pacing pulses and subsequently delivering a firstventricular pacing pulse for the series of ventricular pacing pulsesthat is synchronized with the series of atrial pacing pulses; and afterdelivering the series of atrial pacing pulses and the series ofventricular pacing pulses to the heart, delivering a defibrillationpulse to the heart.
 50. The method of claim 49, wherein delivering afirst atrial pacing pulse for the series of ventricular pacing pulsesincludes delivering a first atrial pacing pulse during a detectedventricular R-wave.
 51. A method, comprising: delivering a series ofatrial pacing pulses and a series of ventricular pacing pulses to aheart that is experiencing supraventricular tachyarrhythmia, whichincludes synchronizing the series of atrial pacing pulses and the seriesof ventricular pacing pulses, which includes delivering a final atrialpacing pulse and a final ventricular pacing pulse substantiallysimultaneously; and after delivering the series of atrial pacing pulsesand the series of ventricular pacing pulses to the heart, delivering adefibrillation pulse to the heart.
 52. A method, comprising: deliveringa series of atrial pacing pulses and a series of ventricular pacingpulses to a heart that is experiencing supraventricular tachyarrhythmia,which includes delivering the series of atrial pacing pulses and theseries of ventricular pacing pulses over a programmable pacing schemeduration, which includes delivering the series of atrial pacing pulsesand the series of ventricular pacing pulses over a programmable rangebetween 2 and 30 seconds; and after delivering the series of atrialpacing pulses and the series of ventricular pacing pulses to the heart,delivering a defibrillation pulse to the heart.
 53. A method,comprising: delivering a series of atrial pacing pulses and a series ofventricular pacing pulses to a heart that is experiencingsupraventricular tachyarrhythmia, which includes delivering aprogrammable number of atrial pulses; and after delivering the series ofatrial pacing pulses and the series of ventricular pacing pulses to theheart, delivering a defibrillation pulse to the heart.
 54. The method ofclaim 53, wherein delivering a programmable number of atrial pulsesincludes delivering a number of atrial pulses in the range between 10and 1000 pulses.
 55. The method of claim 53, wherein delivering aprogrammable number of atrial pulses includes delivering a number ofatrial pulses in the range between 20 and 70 pulses.
 56. The method ofclaim 53, wherein delivering a programmable number of atrial pulsesincludes delivering a number of atrial pulses in the range between 30 to50 pulses.
 57. A method, comprising: delivering a series of atrialpacing pulses and a series of ventricular pacing pulses to a heart thatis experiencing supraventricular tachyarrhythmia, which includesdelivering a series of atrial pacing pulses at a programmable interval,which includes delivering atrial pulses at a programmable intervalbetween 20 and 50 milliseconds per pacing pulse; and after deliveringthe series of atrial pacing pulses and the series of ventricular pacingpulses to the heart, delivering a defibrillation pulse to the heart. 58.A method, comprising: delivering a series of atrial pacing pulses and aseries of ventricular pacing pulses to a heart that is experiencingsupraventricular tachyarrhythmia, which includes delivering atrialpacing pulses with a programmable energy level; and after delivering theseries of atrial pacing pulses and the series of ventricular pacingpulses to the heart, delivering a defibrillation pulse to the heart. 59.A method, comprising: delivering a series of atrial pacing pulses and aseries of ventricular pacing pulses to a heart that is experiencingsupraventricular tachyarrhythmia, which includes delivering ventricularpacing pulses at a programmable rate, which includes deliveringventricular pacing pulses at a pacing rate that is at least 10 beats perminute above an intrinsic ventricular rate; and after delivering theseries of atrial pacing pulses and the series of ventricular pacingpulses to the heart, delivering a defibrillation pulse to the heart. 60.A method, comprising: delivering a series of atrial pacing pulses and aseries of ventricular pacing pulses to a heart that is experiencingsupraventricular tachyarrhythmia; after delivering the series of atrialpacing pulses and the series of ventricular pacing pulses to the heart,delivering a defibrillation pulse to the heart; monitoring the heart todetect a premature ventricular contraction; and upon detecting apremature ventricular contraction, delivering the series of atrialpacing pulses and the series of ventricular pacing pulses to the heartagain prior to delivering the defibrillation pulse to the heart.
 61. Amethod, comprising: delivering a series of atrial pacing pulses and aseries of ventricular pacing pulses to a heart that is experiencingsupraventricular tachyarrhythmia; after delivering the series of atrialpacing pulses and the series of ventricular pacing pulses to the heart,delivering a defibrillation pulse to the heart; monitoring the heart todetect a premature ventricular contraction; and upon detecting apremature ventricular contraction, delivering a programmable number ofadditional atrial pacing pulses and ventricular pacing pulses to theheart prior to delivering the defibrillation pulse to the heart.
 62. Amethod, comprising: analyzing ventricular and atrial cardiac signals todetect supraventricular tachyarrhythmia; delivering a series of atrialpacing pulses and a series of ventricular pacing pulses to a heart thatis experiencing supraventricular tachyarrhythmia; after delivering theseries of atrial pacing pulses and the series of ventricular pacingpulses to the heart, delivering a defibrillation pulse to the heart. 63.A method, comprising: delivering a series of atrial pacing pulses and aseries of ventricular pacing pulses to a heart that is experiencingsupraventricular tachyarrhythmia; and after delivering the series ofatrial pacing pulses and the series of ventricular pacing pulses to theheart, delivering a defibrillation pulse to the heart, whereindelivering a defibrillation pulse to the heart after delivering theatrial pacing pulses and ventricular pacing pulses to the heart includesdelivering the defibrillation pulse to the heart at a predeterminedcoupling interval after delivering a final atrial pacing pulse in theseries of atrial pacing pulses and a final ventricular pacing pulse inthe series of ventricular pacing pulses.
 64. The method of claim 63,wherein delivering the defibrillation pulse to the heart at apredetermined coupling interval occurs outside of a ventricular T-wavewhich reduces the likelihood of inducing ventricular fibrillation. 65.The method of claim 63, wherein delivering the defibrillation pulse tothe heart at a predetermined coupling interval includes delivering thedefibrillation pulse to the heart at a programmable range between 20 and150 milliseconds after delivering the final atrial pacing pulse and thefinal ventricular pacing pulse.
 66. The method of claim 63, whereindelivering the defibrillation pulse to the heart at a predeterminedcoupling interval time includes delivering a programmable electricalenergy pulse between 1 and 10 Joules.